\documentclass{article}
\usepackage{fp}
\input pstfig
\begin{document}
\vspace*{3cm}
$
\def\myR{4}
\def\mytheta{80}
\def\myr{3.9}
\FPeval\myrr{round(\myr * cos(\mytheta / 180 * \FPpi) : 6)}
\FPeval\myl{root(2, \myR * \myR - \myr * \myr)}
\FPeval\myH{round(\myl * sin(\mytheta / 180 * \FPpi) : 6)}
\FPeval\myalpha{arcsin(\myl / (\myR * sin(\mytheta / 180 * \FPpi))) / \FPpi * 180}
\FPeval\myangA{round(\myalpha : 6)}
\FPeval\myangB{round( (180 -  \myalpha) : 6)}
\FPeval\myangC{round( arccos( \myR * cos(\myalpha / 180 * \FPpi) / \myr ) / \FPpi * 180 : 6)}
\FPeval\myangD{round( (180 -  \myangC) : 6)}
\def\myr@{2.8}
\FPeval\myrr@{round(\myr@ * cos(\mytheta / 180 * \FPpi) : 6)}
\FPeval\myl@{root(2, \myR * \myR - \myr@ * \myr@)}
\FPeval\myH@{round(\myl@ * sin(\mytheta / 180 * \FPpi) : 6)}
\FPeval\myalpha@{arcsin(\myl@ / (\myR * sin(\mytheta / 180 * \FPpi))) / \FPpi * 180}
\FPeval\myangA@{round(\myalpha@ : 6)}
\FPeval\myangB@{round( (180 -  \myalpha@) : 6)}
\FPeval\myangC@{round( arccos( \myR * cos(\myalpha@ / 180 * \FPpi) / \myr@ ) / \FPpi * 180 : 6)}
\FPeval\myangD@{round( (180 -  \myangC@) : 6)}
\pnode(0,0){O}
\pnode(\myR; \myangA){A}
\pnode(\myR; \myangB){B}
\pnode(\myR; 90){S}
\pnode(0, \myH){P}
\pnode(0, \myH@){P@}
\qdisk(O){0.5pt}
\psellipticarc(P)(\myr, \myrr){\myangD}{\myangC}
%\psellipticarc(P@)(\myr@, \myrr@){\myangD@}{\myangC@}
\psellipse(P@)(\myr@, \myrr@)
\psarc(O){\myR}{\myangA}{\myangA@}
\psarc(O){\myR}{\myangB@}{\myangB}
\thinline\dashline
\psarc(O){\myR}{\myangB}{\myangA}
\psarc(O){\myR}{\myangA@}{\myangB@}
\psellipticarc(P)(\myr, \myrr){\myangC}{\myangD}
%\psellipticarc(P@)(\myr@, \myrr@){\myangC@}{\myangD@}
\pcline(P)(P@)
\Bput{h}
\pnode(\myr, \myH){C}
\pcline(C)(P)
\mput*{r_2}
\pnode(\myr@, \myH@){C@}
\pcline(C@)(P@)
\mput*{r_1}
\pcline(O)(\myR, 0)
\Bput{R}
$
\end{document}

